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排序方式: 共有552条查询结果,搜索用时 15 毫秒
481.
Clive Finlayson José Carrión Kimberly Brown Geraldine Finlayson Antonio Sánchez-Marco Darren Fa Joaquín Rodríguez-Vidal Santiago Fernández Elena Fierro Marco Bernal-Gómez Francisco Giles-Pacheco 《Quaternary Science Reviews》2011,30(11-12):1525-1532
Although hardly applied to human palaeoecology, bird fossils offer a unique opportunity for quantitative studies of the hominin habitat. Here we reconstruct the Homo habitat niche across a large area of the Palaearctic, based on a database of avian fauna for Pleistocene sites. Our results reveal a striking association between Homo and habitat mosaics. A mix of open savannah-type woodland, wetlands and rocky habitats emerges as the predominant combination occupied by Homo across a wide geographical area, from the earliest populations of the Lower Palaeolithic to the latest hunter-gatherer communities of the Upper Palaeolithic. This observation is in keeping with the view that such landscapes have had long standing selective value for hominins. 相似文献
482.
D. Moret‐Fernández J. Vicente B. Latorre F. Lera C. Castañeda M. V. López J. Herrero 《水文研究》2012,26(2):246-254
The water retention curve (θ(ψ)), which defines the relationship between soil volumetric water content (θ) and matric potential (ψ), is of paramount importance in characterizing the hydraulic behaviour of soils. However, few methods are so far available for estimating θ(ψ) in undisturbed soil samples. We present a new design of TDR‐pressure cell (TDR‐Cell) for estimating θ(ψ) in undisturbed soil samples. The TDR‐Cell consists of a 50‐mm‐long and 50‐mm internal diameter stainless steel cylinder (which constitutes the outer frame of a coaxial line) attached to a porous ceramic disc and closed at the ends with two aluminium lids. A 49‐mm‐long and 3‐mm‐diameter stainless steel rod, which runs longitudinally through the centre of the cylinder, constitutes the inner rod of a coaxial TDR probe. The TDR‐Cell was used to determine the θ(ψ) curves of a packed sand and seven undisturbed soil samples from three profiles of agricultural soils. These θ(ψ) curves were subsequently compared to those obtained from the corresponding 2‐mm sieved soils using the pressure plate method. Measurements of bulk electrical conductivity, σa, as a function of the water content, σa(θ), of the undisturbed soil samples were also performed. An excellent correlation (R2 = 0·988) was found between the θ values measured by TDR on the different undisturbed soils and the corresponding θ obtained from the soil gravimetric water content. A typical bimodal θ(ψ) function was found for most of the undisturbed soil samples. Comparison between the θ(ψ) curves measured with the TDR‐Cell and those obtained from the 2‐mm sieved soils showed that the pressure plate method overestimates θ at low ψ values. The σa(θ) relationship was well described by a simple power expression (R2 > 0·95), in which the power factor, defined as tortuosity, ranged between 1·18 and 3·75. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
483.
Vicente de P. Rodrigues da Silva Adelgicio F. Belo Filho Vijay P. Singh Rafaela S. Rodrigues Almeida Bernardo B. da Silva Inajá F. de Sousa 《水文科学杂志》2017,62(7):1029-1038
Using the Shannon entropy, the space–time variability of rainfall and streamflow was assessed for daily rainfall and streamflow data for a 10-year period from 189 stations in the northeastern region of Brazil. Mean values of marginal entropy were computed for all observation stations and entropy maps were then constructed for delineating annual and seasonal characteristics of rainfall and streamflow. The Mann-Kendall test was used to evaluate the long-term trend in marginal entropy as well as relative entropy for two sample stations. The marginal entropy values of rainfall and streamflow were higher for locations and periods with the highest amounts of rainfall. The entropy values were higher where rainfall was higher. This was because the probability distributions of rainfall and the resulting streamflow were more uniform and less skewed. The Shannon entropy produced spatial patterns which led to a better understanding of rainfall and streamflow characteristics throughout the northeastern region of Brazil. The total relative entropy indicated that rainfall and streamflow carried the same information content at annual and rainy season time scales. 相似文献
484.
Hellen Kezia Silva Almada Divino Vicente Silvério Marcia Nunes Macedo Leonardo Maracahipes-Santos Elizabete Carolina Pinheiro Zaratim Karina Pinheiro Zaratim 《水文科学杂志》2019,64(5):620-632
Water quality in streams is determined by several factors, including geology, topography, climate, and anthropogenic changes. This study aimed to assess the effects of watershed physical, morphology, and precipitation seasonality on the water quality of two streams that supply drinking water to rural settlements and urban areas in the Cerrado-Amazonia transition region. We monitored 16 physico-chemical attributes of water at six different sample locations over three years (2013–2016). Our results indicate that eight of these physico-chemical attributes did not meet the standards for safe drinking water established by Brazilian legislation. Precipitation seasonality, degradation of riparian zones, stream length, and watershed slope were the most important predictors of impaired water quality. Our results highlight the importance of restoring and conserving riparian forests in order to maintain drinking water quality. 相似文献
485.
Maia M. Moreira N. Vicente S. Mirão J. Noronha F. Nogueira P. 《Geology of Ore Deposits》2020,62(6):508-534
Geology of Ore Deposits - The Mociços Cu-deposit is part of a cluster of ancient copper mines in the Sousel-Barrancos metallogenic belt in the Ossa-Morena Zone at the SW Iberia. The orebodies... 相似文献
486.
R. O. Vicente 《Astronomische Nachrichten》1984,305(1):31-32
The campaigns of the programme of international cooperation, called MERIT, for the determination of the earth rotation parameters are reviewed, especially about the difficulties to infer results about polar motion from such short intervals of observations. It is pointed out the need to employ the same models and standards in order to facilitate the comparison of data obtained by classical and modern techniques. 相似文献
487.
This paper describes methods for combining independent observations of polar motion into a single time series, and applies these methods to satellite laser ranging, Doppler, and astrometric polar motion data taken over the period 1981--1983. The polar motion data are treated as complex valued time series, yielding one estimate of the noise level for each series, rather than a separate estimate for X and Y components. Estimates of the noise level which take advantage of the existence of simultaneous observations are preferred. Linear combination of the data may be performed in both the time and the frequency domain, and examples of each are present. The results of analyzing three years of observations show little difference between the Allan and conventional variance. Present day Doppler determinations do not show marked improvement compared to classical astrometric results. Thus, the astrometric observations are still useful. 相似文献
488.
Received: 3 May 1999 · Accepted: 13 July 1999 相似文献
489.
The infralittoral prograding wedge: a new large-scale progradational sedimentary body in shallow marine environments 总被引:1,自引:1,他引:0
F. J. Hernández-Molina L. M. Fernández-Salas F. Lobo L. Somoza V. Díaz-del-Río J. M. Alveirinho Dias 《Geo-Marine Letters》2000,20(2):109-117
A progradational sedimentary body, the infralittoral prograding wedge (IPW), has been developing from the mean fair-weather
wave-base level to the storm wave-base level between the onshore (beach) and the offshore (inner continental shelf) depositional
zones along the Spanish coast during the Late Holocene. The main sedimentary body is composed of large inclined master beds
which prograde seawards parallel to the shoreline, formed by sediments swept offshore by waves from shallow-water littoral
environments. The inclined beds downlap onto finer-grained offshore sediments and, in turn, are overlain by shoreface deposits.
The IPW is generated by downwelling storm currents and associated seaward transport of sediment. It represents a new depositional
model for clastic wave-dominated coasts, and its identification requires a new subdivision of the nearshore environment.
Received: 10 June 1999 / Revision accepted: 15 February 2000 相似文献
490.